1. Field of the Invention
The invention relates to a personal care cleansing agent based on an aqueous solution of a mixture of betaines and anionic compounds.
2. Description of the Prior Art
In particular, the use of combinations of certain betaines and anionic compounds as bath additives is known. For example, it is known to use:
(a) betaines of the general formula EQU R.sup.1 N.sup..sym. R.sup.2 R.sup.3 (CH.sub.2).sub.y COO.sup..crclbar.(I) PA1 (b) one or more anionic compounds from the group of sodium or ammonium alkyl ether sulfate, alkanolamine alkyl ether sulfate, alkanolamine alkyl sufate, in which the alkyl group has 8 to 14 carbon atoms, PA1 R.sup.6 and R.sup.7 are the same or different and represent alkyl or hydroxyalkyl radicals with 1 to 4 carbon atoms, PA1 n=2 or 3, and PA1 m=1, 2, 3 or 4.
in which
R.sup.1 is an alkyl radical of a fatty acid with 6 to 18 carbon atoms or the R.sup.4 CONH(CH.sub.2).sub.x radical, in which PA2 R.sup.2 and R.sup.3 are the same or different and represent alkyl radicals with 1 to 4 carbon atoms and PA2 y=1, 2, or 3, in combination with,
R.sup.4 is an alkyl radical of a fatty acid with 6 to 18 carbon atoms, and PA3 x=2 or 3,
in a weight ratio of a:b from 3:7 to 7:3.
Betaines of formula I have been used for some time and, to an increasing extent, for the preparation of shower gels, hair shampoos, bath additives and similar cosmetic preparations.
For this purpose, betaines of the general formula ##STR1## have proven themselves particularly useful. In these betaines, R.sup.5 represents the alkyl radical of a fatty acid with 10 to 18 carbon atoms,
The use of such betaines as bath additives is described in German Patent 1,172,802. However, it turned out in practice that betaines of formula II can occasionally cause skin irritations, and especially irritations of the mucous membranes in people with sensitive skin.
A process was therefore developed as disclosed in German patent application No. P 29 26 479.7-42 wherein during the entire course of the reaction, the quaternization reaction is carried out in an alkaline solution which has a pH of 7.5 to 10, measured at 98.degree. C. The betaines, so prepared, are essentially free of unreacted fatty acid amide dialkylamines and organically linked chlorine. The products show an improved mucous membrane compatibility.
Surprisingly, it has now turned out that these betaines, which are obtained in a purer form than those of the state of the art, cannot be thickened by conventional means, i.e., by the addition of anionic compounds, such as, sodium or ammonium alkyl ether sulfate, alkanolamine alkyl ether sulfate, or alkanolamine alkyl sulfate, in which the alkyl group has 8 to 14 carbon atoms.
For many application purposes, however, it is essential that the aqueous solutions of the betaines have an increased viscosity, especially, for example, for the preparation of shower gels or hair shampoos. The thickening of betaines of the general formula I, in which the R.sup.1 is the alkyl radical of a fatty acid with 6 to 18 carbon atoms, also creates the same difficulties.